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  • Springer  (592)
  • Blackwell Science Ltd
  • 2000-2004  (152)
  • 1990-1994  (374)
  • 1965-1969  (74)
  • 1935-1939  (18)
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  • 1
    Electronic Resource
    Electronic Resource
    Metal substitution in transferrins: specific binding of cerium(IV) revealed by the crystal structure of cerium-substituted human lactoferrin (2000)
    Springer
    JBIC 5 (2000), S. 692-698 
    Details
    ISSN: 1432-1327
    Keywords: Metal substitution Cerium binding Lactoferrin Crystal structure Transferrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Proteins of the transferrin family play a key role in iron homeostasis through their extremely strong binding of iron, as Fe3+. They are nevertheless able to bind a surprisingly wide variety of other metal ions. To investigate how metal ions of different size, charge and coordination characteristics are accommodated, we have determined the crystal structure of human lactoferrin (Lf) complexed with Ce4+. The structure, refined at 2.2 Å resolution (R=20.2%, R free=25.7%) shows that the two Ce4+ ions occupy essentially the same positions as do Fe3+, and that the overall protein structure is unchanged; the same closed structure is formed for Ce2Lf as for Fe2Lf. The larger metal ion is accommodated by small shifts in the protein ligands, made possible by the presence of water molecules adjacent to each binding site. The two Ce4+ sites are equally occupied, indicating that the known difference in the pH-dependent release of Ce4+ arises from a specific protonation event, possibly of the His ligand in one of the binding sites. Comparing the effects of binding Ce4+ with those for the binding of other metal ions, we conclude that the ability of transferrins to accommodate metal ions other than Fe3+ depends on an interplay of charge, size, coordination and geometrical preferences of the bound metal ion. However, it is the ability to accept the six-coordinate, approximately octahedral, site provided by the protein that is of greatest importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750000157
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  • 2
    Electronic Resource
    Electronic Resource
    Ecological and evolutionary implications of digestive processes: Bird preferences and the sugar constituents of floral nectar and fruit pulp (1992)
    Springer
    Cellular and molecular life sciences 48 (1992), S. 544-551 
    Details
    ISSN: 1420-9071
    Keywords: Bird feeding preferences ; digestion ; intestinal enzymes ; sucrase ; fruit ; nectar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Plants pollinated and dispersed by different groups of birds offer different kinds of sugars in nectar and fruit pulp. The preferences and physiological traits of avian pollinators and seed dispersers are broadly correlated with the sugar composition of the nectar and fruit that they feed on and appear to have influenced the evolution of the sugar composition of the rewards that plants offer. Hummingbirds prefer sucrose whereas many nectar- and fruit-eating passerines prefer glucose and fructose. Preference for hexoses in passerines seems to be associated with poor sucrose assimilation resulting from two physiological mechanisms: lack of intestinal sucrase activity and fast passage rates. Sucrase activity absence appears to be restricted to a single phylogenetic group (the sturnid-muscicapid lineage). Fast passage rates seem to be characteristic of many small frugivores and to hinder the assimilation of complex nutrients that require hydrolysis before absorption. Hummingbirds have extremely specialized digestive traits that allow them to assimilate sucrose at high rates and with extremely high efficiency. These specialized digestive traits appear not to be present in many nectar-feeding passerines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01920237
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  • 3
    Electronic Resource
    Electronic Resource
    Technical Opportunities for International Collaborations by the U.S. Fusion Program (2000)
    Springer
    Journal of fusion energy 19 (2000), S. 65-79 
    Details
    ISSN: 1572-9591
    Keywords: Fusion energy ; international collaboration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This report was prepared by a Working Group at the request of the U.S. Department of Energy, Office of Fusion Energy Sciences in 1997. The report addresses technical opportunities for mutually beneficial collaboration between the United States and other international fusion research programs. A number of outstanding opportunities are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012281826821
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  • 4
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    Ecological and evolutionary implications of digestive processes: Bird preferences and the sugar constituents of floral nectar and fruit pulp (1992)
    Springer
    Details
    Publication Date: 1992-06-01
    Print ISSN: 0014-4754
    Topics: Biology , Medicine
    Published by Springer
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    PAPER CURRENT
  • 5
    Electronic Resource
    Electronic Resource
    Differential lifetime success and performance of native and non-native Atlantic salmon examined under communal natural conditions (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The lifetime success and performance characteristics of communally reared offspring of wild native Burrishoole (native), ranched native (ranched) and non-native (non-native) Atlantic salmon Salmo salar from the adjacent Owenmore River were compared. Non-native 0+ year parr showed a substantial downstream migration, which was not shown by native and ranched parr. This appears to have been an active migration rather than competitive displacement and may reflect an adaptation to environmental or physiographic conditions within the Owenmore River catchment where the main nursery habitat is downstream of the spawning area. There were no differences between native and ranched in smolt output or adult return. Both of these measures, however, were significantly lower for the non-native group. A greater proportion of the non-native Atlantic salmon was taken in the coastal drift nets compared to the return to the Burrishoole system, probably as a result of the greater size of the non-native fish. The overall lifetime success of the non-native group, from fertilized egg to returning adult, was some 35% of native and ranched. The ranched group showed a significantly greater male parr maturity, a greater proportion of 1+ year smolts, and differences in sex ratio and timing of freshwater entry of returning adults compared to native, which may have fitness implications under specific conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00557.x
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  • 6
    Electronic Resource
    Electronic Resource
    Body condition and reproductive capacity of three-spined stickleback infected with the cestode Schistocephalus solidus (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 64 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relationship between reproductive ability and the residual index of body condition in three-spined stickleback Gasterosteus aculeatus from a population infected with the cestode macroparasite Schistocephalus solidus in Walby Lake, Alaska, was examined. In general, reproductive activities resulted in significantly lower levels of body condition in three-spined stickleback during the latter part of the breeding season, and relatively high levels of S. solidus infection intensified the energetic drain. Although female body condition did not differ significantly due just to the presence of S. solidus, increased parasite index did have a significant negative effect on female body condition. Males showed significantly lower levels of body condition in response to S. solidus infection alone and in association with a greater parasite index. Males had greater mean parasite indices than females. Females had significantly lower body condition than males, which may be due to discrepancies in energy expenditure between the sexes during reproduction. Females with greater body condition were significantly more likely to produce a clutch of eggs than those with lower condition, suggesting a threshold effect of body condition on reproductive capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00411.x
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  • 7
    Electronic Resource
    Electronic Resource
    Human milk lactoferrin is a serine protease that cleaves Haemophilus surface proteins at arginine-rich sites (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 47 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Lactoferrin is a member of the lactotransferrin family of non-haem, iron-binding glycoproteins and is found at high concentrations in all human secretions, where it plays a major role in mucosal defence. In recent work, we observed that lactoferrin has proteolytic activity and attenuates the pathogenic potential of Haemophilus influenzae by cleaving and removing two putative colonization factors, namely the IgA1 protease protein and the Hap adhesin. Experiments with protease inhibitors further suggested that lactoferrin may belong to a serine protease family. In the present study we explored the mechanism of lactoferrin protease activity and discovered that mutation of either Ser259 or Lys73 results in a dramatic decrease in proteolysis. Examination of the crystal structure revealed that these two residues are located in the N-terminal lobe of the protein, adjacent to a 12–15 Å cleft that separates the N-lobe and the C-lobe and that can readily accommodate large polypeptide substrates. In additional work, we found that lactoferrin cleaves IgA1 protease at an arginine-rich region defined by amino acids 1379–1386 (RRSRRSVR) and digests Hap at an arginine-rich sequence between amino acids 1016 and 1023 (VRSRRAAR). Based on our results, we conclude that lactoferrin is a serine protease capable of cleaving arginine-rich sequences. We speculate that Ser259 and Lys73 form a catalytic dyad, reminiscent of a number of bacterial serine proteases. In addition, we speculate that lactoferrin may cleave arginine-rich sequences in a variety of microbial virulence proteins, contributing to its long-recognized antimicrobial properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03327.x
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  • 8
    Electronic Resource
    Electronic Resource
    Coupled biogeochemical and hydrological responses of streams and rivers to drought (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 〈list xml:id="l1" style="custom"〉1Severe or extreme droughts occurred about 10% of the time over a 105-year record from central New Mexico, U.S.A., based on the Palmer Drought Severity Index.2Drought lowers water tables, creating extensive areas of groundwater recharge and fragmenting reaches of streams and rivers. Deeper groundwater inputs predominate as sources of surface flows during drought. Nutrient inputs to streams and rivers reflect the biogeochemistry of regional ground waters with longer subsurface residence times.3Inputs of bioavailable dissolved organic carbon to surface waters decrease during drought, with labile carbon limitation of microbial metabolism a byproduct of drought conditions.4Decreased inputs of organic forms of carbon, nitrogen and phosphorus and a decrease in the organic : inorganic ratio of nutrient inputs favours autotrophs over heterotrophs during drought.5The fate of autotrophic production during drought will be strongly influenced by the structure of the aquatic food web within impacted sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01082.x
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrological variability, organic matter supply and denitrification in the Garonne River ecosystem (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Groundwater nitrate contamination has become a worldwide problem as increasing amounts of nitrogen fertilisers are used in agriculture. Alluvial groundwater is uniquely juxtaposed between soils and streams. Hydrological connections among these subsystems regulate nutrient cycling.2. We measured denitrification using an in situ acetylene-block assay in a nitrate-contaminated portion of the Garonne River catchment along a gradient of surface water–ground water mixing during high (snowmelt) and low flow.3. During high flow (mid-April to early June) the water table rose an average of 35 cm and river water penetrated the subsurface to a great extent in monitoring wells. Denitrification rates averaged 5.40 μgN2O L−1 min−1 during the high flow period, nearly double the average rate (2.91 μgN2O L−1 min−1) measured during base flow. This was driven by a strong increase in denitrification in groundwater under native riparian vegetation. Nitrate concentrations were significantly lower during high flow compared with base flow. Riparian patches had higher dissolved organic carbon concentrations that were more aromatic compared with the gravel bar patch closest to the river.4. Multiple linear regression showed that the rate of denitrification was best predicted by the concentration of low molecular weight organic acids. These molecules are probably derived from decomposition of soil organic matter and are an important energy source for anaerobic respiratory processes like denitrification. The second best predictor was per cent surface water, reflecting higher denitrification rates during spring when hydrological connection between surface water and ground water was greatest.5. Our results indicate that, while denitrification rates in Garonne River alluvium were spatially and temporally variable, denitrification was a significant NO3 sink during transport from the NO3-contaminated floodplain to the river. DOC availability and river–floodplain connectivity were important factors influencing observed spatial and temporal patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2426.2003.01175.x
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  • 10
    Electronic Resource
    Electronic Resource
    Simulated variations in atmospheric CO2 over a Wisconsin forest using a coupled ecosystem–atmosphere model (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Ecosystem fluxes of energy, water, and CO2 result in spatial and temporal variations in atmospheric properties. In principle, these variations can be used to quantify the fluxes through inverse modelling of atmospheric transport, and can improve the understanding of processes and falsifiability of models. We investigated the influence of ecosystem fluxes on atmospheric CO2 in the vicinity of the WLEF-TV tower in Wisconsin using an ecophysiological model (Simple Biosphere, SiB2) coupled to an atmospheric model (Regional Atmospheric Modelling System). Model parameters were specified from satellite imagery and soil texture data. In a companion paper, simulated fluxes in the immediate tower vicinity have been compared to eddy covariance fluxes measured at the tower, with meteorology specified from tower sensors. Results were encouraging with respect to the ability of the model to capture observed diurnal cycles of fluxes. Here, the effects of fluxes in the tower footprint were also investigated by coupling SiB2 to a high-resolution atmospheric simulation, so that the model physiology could affect the meteorological environment. These experiments were successful in reproducing observed fluxes and concentration gradients during the day and at night, but revealed problems during transitions at sunrise and sunset that appear to be related to the canopy radiation parameterization in SiB2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00613.x
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